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Young Star Really Gets Around

Photonics.comDec 2011
BALTIMORE, Dec. 7, 2011 — The fastest spinning star yet has been discovered, a hot blue giant rotating at a stupefying million miles an hour. Twirling 100 times faster than our sun does, the star VFTS 102 is very close to the limit at which it would be torn apart because of centrifugal forces.

Selma de Mink and Daniel Lennon of the Space Telescope Science Institute in Baltimore are part of the international team of astronomers who used the European Southern Observatory’s Very Large Telescope at the Paranal Observatory in Chile to observe the massive, bright young star, which lies within the neighboring dwarf galaxy, the Large Magellanic Cloud, about 160,000 light-years from Earth. The team believes that the star may have had a violent past, ejected from a double star system after its companion exploded as a supernova.

An artist’s concept depicts the fastest rotating star found to date. Located in the Tarantula Nebula within the Large Magellanic Cloud, the massive, bright young star, called VFTS 102, rotates at a million miles per hour. Centrifugal forces from this dizzying spin rate have flattened the star into an oblate shape and spun off a disk of hot plasma, seen edge on in this view from a hypothetical planet. (Image: NASA, European Space Agency and G. Bacon, Space Telescope Science Institute)
The investigators also found that the star, which is about 25 times more massive than the sun and about 100,000 times brighter, was moving through space at a speed significantly different from its neighbors.

“The remarkable rotation speed and the unusual motion compared to the surrounding stars led us to wonder if this star had an unusual early life. It was suspicious,” said Philip Dufton of Queen’s University Belfast in Northern Ireland, the lead author of a paper presenting the results in Astrophysical Journal Letters.

The team suggests that the star could have started life as one component of a binary star system. If the two stars were close, gas from the companion could have streamed over and, in the process, VFTS 102 would have spun faster and faster. After a short life of about 10 million years, the massive companion would have exploded as a supernova, which would have led to the ejection of VFTS 102 and could explain a second anomaly — the difference between its speed and that of other stars in the region. As it collapsed, the massive companion would then have turned into a pulsar. It is intriguing that there is a nearby supernova remnant and a pulsar. What is not yet clear is whether or not they are related to VFTS 102.

The astronomers cannot yet be sure that this is exactly what happened. However, Dufton said, “this is a compelling story because it explains each of the unusual features that we’ve seen. This star is certainly showing us unexpected sides of the short but dramatic lives of the heaviest stars.”

To test this theory, Lennon and de Mink will use the Hubble Space Telescope to make precise measurements of the star’s proper motion across space.

The scientific observation of celestial radiation that has reached the vicinity of Earth, and the interpretation of these observations to determine the characteristics of the extraterrestrial bodies and phenomena that have emitted the radiation.